Preparation And Functionalization Of High Performance Resins Based On Supermolecular Interaction Between Pyrene Groups

With the continuous progress of science and technology,higher requirements have been put forward for the performance of resins to meet various application scenarios,and materials are developing towards high-performance and multifunctional directions.However,there are often certain contradictions between improving the performance of materials.For example,introducing rigid structures such as benzene rings or cross-linked structures into the system can improve strength and modulus,but this strategy often leads to a decrease in the toughness of the material.In addition,achieving both performance and functionality is a significant challenge,as the integration of functionalities results in material design strategies being one-sided,and the granting of functionality often comes at the expense of mechanical properties.Fluorescent materials can be prepared by introducing rare earth metals,carbon quantum dots,or conjugated structures into polymers,but poor interfacial compatibility between external fluorescent fillers and the matrix can lead to a decrease in the mechanical properties of the resulting polymer.Therefore,endowing materials with multiple functions while enhancing their mechanical properties remains a challenge.In this paper,pyrene group was introduced into epoxy resin and polyurea elastomer in the form of covalent bond,and the mechanical properties of the resin were improved through the strong π-π interaction between pyrene groups,which became physical cross-linking points and energy dissipation units.At the same time,the rigid planar conjugate structure of pyrene group gave the material fluorescence and UV shielding,and realized the synchronous high-performance and multi-function of the material.The main research content and achievements of this paper are as follows:(1)An epoxy resin network containing pyrene side chains was designed and prepared.Through the aggregation and assembly of pyrene side chains,the "internal anti plasticization" mechanism,and the special effect of pyrene groups on ultraviolet light,high-performance and functionalization of epoxy resin were achieved.Pyrene derivatives with a single epoxy group(PrGE)were synthesized using 1-hydroxypyrene as raw material in a one-step method.They were mixed with bisphenol F-type epoxy resin(BPF)and cured with DDM,D230,and D400 curing agents to obtain epoxy resin systems with different stiffness and flexibility.Among them,the pyrene group exists in the form of a hanging chain,which has the effect of "internal anti plasticization",and there are abundant π-π supramolecular forces between the pyrene group.Through DMA,XRD and tensile tests,it was found that the introduction of PrGE can reduce the free volume of the system,increase the cohesive energy,and improve the strength,modulus,and glass transition temperature of the epoxy resin.In addition,the conjugated structure of pyrene groups endows epoxy resin with excellent UV shielding performance,achieving full wavelength absorption of UV light,and is expected to develop new UV shielding coatings.The pyrene group also endows epoxy resin with fluorescence,expanding its application in the field of anti-counterfeiting.(2)A thermoplastic polyurea elastomer(PPU-x)containing pyrene side chains was designed and prepared.High performance and multifunctional polyurea elastomers were obtained through π-πstacking between pyrene side chains,hydrogen bonding,and the special effect of pyrene groups on ultraviolet light.A pyrene derivative(DHPr)containing two hydroxyl groups was synthesized by reacting mercaptoethanol with PrGE.Then,diisocyanate(HMDI)was added to react with polyether amine to produce PPU-x.The π-π stacking interaction between pyrene groups was demonstrated through UV absorption spectroscopy and fluorescence emission spectroscopy.The microphase separation phenomenon of PPU-x was studied through SEM,EDS,and AFM.A polyurea(BPU-x)containing benzyl side chains was synthesized by replacing the side chains with benzyl groups under the same main chain.The tensile properties of the material were tested,and the results showed that the tensile strength of PPU-0.3 was as high as 41 MPa,an increase of 141% compared to the pure polyurea system and491% compared to BPU-0.3.This proves that the improvement in mechanical properties of PPU-x is due to the introduction of pyrene groups.Due to the presence of a large amount of supramolecular forces in the system,PPU-x also exhibits good self-healing performance.Due to the conjugated structure of the pyrene group,PPU-x exhibits UV shielding and fluorescence properties.In addition,based on the structural similarity of pyrene group and graphene and π-π interaction,graphene is well dispersed in the polyurea matrix,and the dielectric constant of graphene modified polyurea nanomaterials is increased by three times.It is used to prepare friction nanogenerator(TENG).The results show that TENG has high sensitivity,stable output performance and good durability,and has broad prospects in signal monitoring and energy storage.